Jack Dorsey, chairman and co-founder of Twitter Inc., left, and and San Francisco Mayor Edward 'Ed' Lee, right, laugh as New York City Mayor Michael 'Mike' Bloomberg speaks during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Jack Dorsey, chairman and co-founder of Twitter Inc., left, and and San Francisco Mayor Edward 'Ed' Lee, right, laugh as New York City Mayor Michael 'Mike' Bloomberg speaks during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Jack Dorsey, chairman and co-founder of Twitter Inc., center, speaks as New York City Mayor Michael 'Mike' Bloomberg, right, and San Francisco Mayor Edward 'Ed' Lee listen during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Jack Dorsey, chairman and co-founder of Twitter Inc., center, speaks as New York City Mayor Michael 'Mike' Bloomberg, right, and San Francisco Mayor Edward 'Ed' Lee listen during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Jack Dorsey, chairman and co-founder of Twitter Inc., right, speaks with New York City Mayor Michael 'Mike' Bloomberg, left, as San Francisco Mayor Edward 'Ed' Lee listens after a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Jack Dorsey, chairman and co-founder of Twitter Inc., right, speaks with New York City Mayor Michael 'Mike' Bloomberg, left, as San Francisco Mayor Edward 'Ed' Lee listens after a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

San Francisco Mayor Edward 'Ed' Lee, left, speaks as Jack Dorsey, chairman and co-founder of Twitter Inc., after a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Michael Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

San Francisco Mayor Edward 'Ed' Lee, left, speaks as Jack Dorsey, chairman and co-founder of Twitter Inc., after a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Michael Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Jack Dorsey, chairman and co-founder of Twitter Inc., left, speaks to the media as New York City Mayor Michael 'Mike' Bloomberg, right, and San Francisco Mayor Edward 'Ed' Lee listen during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Jack Dorsey, chairman and co-founder of Twitter Inc., left, speaks to the media as New York City Mayor Michael 'Mike' Bloomberg, right, and San Francisco Mayor Edward 'Ed' Lee listen during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

San Francisco Mayor Edward 'Ed' Lee, center, speaks as Jack Dorsey, chairman and co-founder of Twitter Inc., left, and New York City Mayor Michael 'Mike' Bloomberg listen during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

San Francisco Mayor Edward 'Ed' Lee, center, speaks as Jack Dorsey, chairman and co-founder of Twitter Inc., left, and New York City Mayor Michael 'Mike' Bloomberg listen during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Jack Dorsey, chairman and co-founder of Twitter Inc., listens during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Jack Dorsey, chairman and co-founder of Twitter Inc., listens during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Jack Dorsey, chairman and co-founder of Twitter Inc., listens during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Jack Dorsey, chairman and co-founder of Twitter Inc., listens during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Jack Dorsey, chairman and co-founder of Twitter Inc., left, and and San Francisco Mayor Edward 'Ed' Lee, right, laugh as New York City Mayor Michael 'Mike' Bloomberg speaks during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Jack Dorsey, chairman and co-founder of Twitter Inc., left, and and San Francisco Mayor Edward 'Ed' Lee, right, laugh as New York City Mayor Michael 'Mike' Bloomberg speaks during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Jack Dorsey, chairman and co-founder of Twitter Inc., center, speaks as New York City Mayor Michael 'Mike' Bloomberg, right, and San Francisco Mayor Edward 'Ed' Lee listen during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Jack Dorsey, chairman and co-founder of Twitter Inc., center, speaks as New York City Mayor Michael 'Mike' Bloomberg, right, and San Francisco Mayor Edward 'Ed' Lee listen during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Jack Dorsey, chairman and co-founder of Twitter Inc., from left, New York City Mayor Michael 'Mike' Bloomberg and San Francisco Mayor Edward 'Ed' Lee arrive at a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Jack Dorsey, chairman and co-founder of Twitter Inc., from left, New York City Mayor Michael 'Mike' Bloomberg and San Francisco Mayor Edward 'Ed' Lee arrive at a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Jack Dorsey, chairman and co-founder of Twitter Inc., left, and and... News PhotoCalifornia,Chairperson,Ed Lee,Finance,Founder,Government,Horizontal,Jack Dorsey,Laughing,Meeting,Michael Bloomberg,New York City,North America,Online Messaging,Politics,Press Conference,San Francisco - California,Social Networking,Summit,Talking,Technology,The Americas,The Internet,Twitter,USAPhotographer BloombergCollection: Bloomberg 2013 BloombergJack Dorsey, chairman and co-founder of Twitter Inc., left, and and San Francisco Mayor Edward 'Ed' Lee, right, laugh as New York City Mayor Michael 'Mike' Bloomberg speaks during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images